Hereinafter, the apparatus and the method for managing the database will be described.
A hierarchical database, which is exemplified by an object-oriented database (OODB) and an object relational database (ORDB), has a hierarchal structure, in which lower classes inherit properties of upper classes. In such a hierarchical database, the number of properties of the lower classes increases with inheritances from the upper classes. The inheritances of the properties of the upper classes to the lower classes are generally called “inheritance,” the feature of which is described in various documents including.
In the OODB, a unit of classification of one level is generally called a “class.” On the other hand, in the ORDB, a table that permits the inheritance corresponds to the class in the OODB. Between the tables with a hierarchical relation, the properties are inherited from upper tables to lower tables, in other words, header information of a column constituting an upper table is inherited to a lower table. Data having the same type of property and belonging to a certain class of each level is called an “instance,” and a collection thereof is called a “population.” The population of data is usually stored in a structure called a table in a relational database (RDB) or an ORDB. A string of properties making up a table is called a header of the table.
One of known hierarchical databases is defined by the ISO13584 Parts Library standard (hereinafter simply referred to as “PLIB” standard), which is an international standard for implementing an electronic catalogue system capable of electronically providing product information. The “PLIB” standard is an international standard consisting of a plurality of “Parts” and defines a manner for object-oriented description of products library data or parts library data and a semantics for file exchange, in other words, defines what kind of terms, manner for description, and data type are to be employed. Part 42 (Part Issue No. 42) of the PLIB has the same contents as the IEC61360-2 (Part Issue No. 2). The standard classifies products in an object-oriented manner, clarifies a group of properties characterizing each class, and achieves file exchange of the contents corresponding to the class, and therefore, the concept of property inheritance is naturally incorporated herein. Further, since the standard is formulated based on the ISO6523 “Structure for Identification of Organizations and Organization Parts,” with the use of the International Code Designator (ICD) defined by ISO6523, in particular, an internationally unique identifier can be allocated to each property.
In recent years, systems based on the PLIB standard are proposed (for example, see Japanese Patent Application Laid-Open No. 2004-177996, and Japanese Patent Application Laid-Open No. 2004-178015).
The PLIB standard defines the data exchange format according to a basic concept that technical information on products should be represented by “dictionary” and “contents.” The “dictionary” described herein is designed so that it may inherit a hierarchical relation and the properties corresponding to each level and therefore, an existing dictionary is usually referenced.
To represent an inter-“dictionary” referencing relation, the PLIB standard employs a “CaseOf” feature. This feature for representing the referencing relation enables the properties previously defined in another “dictionary (a referenced dictionary)” to be taken into the referencing dictionary for further use. The use of “CaseOf” allows for partial inter-class inheritance of the properties. Using the “CaseOf” feature to import and export a lot of properties, the same properties imported or exported may be used in another dictionary and therefore, such advantages are attained that actual product data exchange is facilitated and the need for preparing the dictionary is eliminated.
The referencing relation may be established with the inclusion of description of a Basic Semantic Unit (BSU) as a pointer in the referencing dictionary. The BSU is an identifier assigned to each of the classes or properties defined in the referenced dictionary.
There lies a problem, however, in that on the referencing dictionary side alone, any detailed information characterizing the imported properties including the name, definition, data type, and unit cannot be known. Accordingly, in order to acquire the detailed information on the imported property on the side of the referencing dictionary, the imported property in the referenced dictionary must be searched and information must be retrieved therefrom.
Usually, the referenced dictionary is an international standard defining a huge amount of classes and properties, while the properties to be referenced occupy just a small part therein, and therefore, an efficient scheme for inter-dictionary data communication is desired.
The present invention is devised to resolve the aforementioned problems and therefore, an object of the present invention is to provide an apparatus and a method for managing a database, which enables the detailed information on the imported property to be acquired on the referencing dictionary side and inter-dictionary data communication to be effectively performed.